Shockproof radiographic tube



Dec. 27, 1938.

M. J. GROSS ET AL sHocKPRooF RADIOGRAPHIC TUBE 3 Sheets-Sheetl l Filed March 22, 1955 H .JE

INVENTOR HALVEEHN d. @R055 BY Z D d. ATLEE ATTORN Dec. 27, 1938 M. J. GROSS L=:r` AL- 1 2,141,860

l SHOCKPROOF RADIOGRAPHIC TUBE 5 Sheets-Sheet 2 ,Filed March 22, 19 5 FIC-21.5

INVENTOR MALVERN u. @2055 ZED d. TLEE BY A TTORNEY Dec. 27, 1938. M. J, GROSSl ET AL 2,141,860

SHOCKPRQOF RADTOGRAPHTC TUBE Filed March 22. 1935 3 Sheets-Sheet 3 INVENTOR MALVERN Ll- @R055 2E@ J. ATL E BY, /7

ATTORN Y Patented Dec. 27, 1938 UNITED STATES "PATENT OFFICE SHOCKPROOF RADIOGRAPHIC Application March 22, 1935, Serial No. 12,428

13 Claims.

The present invention relates to X-ray apparatus and particularly to an improved insulating and cooling jacket for an X-ray tube.

The objects of the invention include, among others, the provision of:

An X-ray tube so protected that it is capable of withstanding large amounts of energy and operating eiiciently Within a body of oil or similar cooling and insulating material;

An enclosure for an X-ray tube arranged to hold insulating oil Within a grounded metallic casing and providing means for taking up the expansion of the insulating oil under heat, such means to include either an expansion chamber 15 containing an expansion and contraction device open to the atmosphere, or an ordinary expansion chamber connected to the tube enclosure by means of a conduit;

An X-ray tube having protection thereabout zo comprising a grounded casing completely enclosing the tube save for an opening provided for the emergence of a useful beam of X-light;

Means for positioning and locating an X-ray tube so that it may be accurately located within a container;

A novel cathode base for an X-ray tube so arranged that the contact points covered by it can be adjusted after the base has been cemented or otherwise affixed to the tube;

A novel arrangement of insulators and connectors whereby electrical energy for activating an X-ray tube may be carried within the body of a casing; and

A novel radiator for removing heat from the 35 anode of a tube and so. designed that it will give a maximum volume to the radiatorwhile imposing a minimum strain on the insulation between the radiator and the inner surface of the container.

These objects and such other objects as may hereinafter appear are obtained by the novel construction, unique arrangement and improved combination of elements which constitute the invention, one form of which is illustrated in the accompanying three sheets of drawings hereby made a part of this specification.

In the drawings:

Figure 1 is a transverse section of a tube and ,o a housing therefor constructed in accord with the invention.

Figure 2 is an exploded perspective of the cathode energizing and tube locating means shown in the section at the left hand side of L5 Figure l.

(Cl. Z50- 88) Figure 3 is a transverse section along the line 3 3 of Figure 1.

Figure 4 is a transverse section of one of the cables made in accordance with the invention and taken along the line 4-4 of Figure 1.

Figure 5 is a perspective view of the protecting collars and locks used at the ends of the X-ray tube.

Figure 6 is a diagrammatic representation of the circuits to a tube having exterior to the tube casing a switching device for energizing one cathode or the other, an expansion device being shown attached to the casing.

Figure 7 is a view similar to that in Figure 6 but with the change-over or switching device disposed within the casing and the expansion device separate from the casing but connected thereto by means of a iiexible tubing.

Like reference characters are used to designate similar parts in the drawings and in the description that follows.

Reference should be had rst to Figure 1. A

container I encloses an X-ray tube II. The X- ray tube II has an anode I2 and a cathode I3. The anode comprises an anode head I4 made of copper or other suitable material in which a tungsten button I is embedded in a manner well-known in the art. The head I4 is upon a shank I6 and is attached thereto in any suitable manner, as for instance, by means of the complemental screw threads I1.

The shank I6 has a passage I8 to permit air to escape from between the anode head I4 and the forward end of the anode shank I6 as these two parts are assembled by screwing one into the other. The passage I8 is provided so that close and intimate contact may be had between the opposing surfaces of the anode head I4 and anode stem IB.

A nickel steel sleeve I9 is attached to the an ode head I4 in any manner desirable, such as by soldering. The sleeve I9 may be made in accordance with the particulars given in a copend ing application for Letters Patent, entitled X-ray tube, Serial Number 715,902, led March 16, 1934 by Malvern J. Gross and Zed J. Atlee, and comprises a satisfactory jointure between the glass of the tube and the metal portions of the anode. The glass to metal joint between tube and sleeve is indicated at 20. In the manner illustrated, the anode head I4 and with it the anode shank I6 are supported within the envelope of the X-ray tube.

A second metallic tube or sleeve 2| also made of nickel steel or other suitable metal is secured to the anode head I4 in any desirable manner, as for instance, by means of screws 22. The tube or sleeve 2i aids in blocking up the anode arm of the X-ray tube and also shields the glass-tometal joint 23 from stray electron bombardment which might cause disintegration of the glass to metal seal.

'I'he tube has an envelope 23 which comprises an anode extension 24 having .a reentrant portion 25 to which the glass-to-metal seal 23 is made. The envelope includes an enlarged central section 25 which forms what is known as the bulb portion of the tube.

Opposite the anode extension 24, there is a cathode extension 21. Extension 21 has a reentrant portion 23 in which an inverted pinch seal 29 is located.. The seal-of! of the tube is indicated at 33.

'I 'he pinch seal 23 is made in a manner well known in the art. Through it passes conductors for energizing the filaments forming a portion of the cathode that will be described later.

The cathode I3 consists essentially of a cathode cup 3i. The cathode cup 3i has a plurality of filaments, 32 and 33. These illaments are for the purpose of converting the X-ray tube from one having a large focal spot and using a high energy unit to a tube having a small :focal spot and employing a small energy unit, or vice versa, for purposes which are well understood by anyone skilled in the X-ray art.

While the drawings illustrate but two illaments and hence the possibility of two focal spots of different sizes, it is to be understood that a construction similar to that shown may be readily made to increase the number oi focal spots to say, three, four, ilve, or more.

The iilaments 32 and 33 are surrounded by depressed focusing openings 34 and 35, respectively, the cups being constructed and operating in a manner well-known in the art. Circuits for use with the several laments 32 and 33 will be more fully described later in this specification in connection with a device herein disclosed for shifting energy from one filament to the other.

The cathode arm 21 of the X-ray tube has attached to it, as by cementing or any similar process, a cup 36, to which a plate 35a is attached by means of screws i90, which pass through arc-shaped slots ISI in the plate 33a and are screwed into threaded holes in bosses in cup 36. The arc-shaped slots ISI are made somewhat wider than necessary for the screws l33, so as to permit adjustment of the plate 35a on the cup 36 in a single plane for a Purpose later to be described.

Plate 35a has located on it contact points 31, 38, and 39 (see Figure 2) to which the terminals of the two filaments 32 and 33 are connected.

The tube enclosure or casing Iii consists essentially of an outer body 43 of a conductive material such as aluminum. The inner surfaces of the enclosure or casing iii are sealed against oil leakage by means of several coats of a suitable material or compound such as Glyptol, Bakelite varnish, etc. Such sealing material is indicated 4i. The casing 40 has a central section 42 oi' a generally cylindrical form and two irregular shaped end pieces of larger diameter, 43 and 43a, respectively.

The central cylindrical section 42 forms a main support for the X-ray tube il. An insulating sleeve 44 of Bakelite or similar material closely surrounds the bulb section 23 of envelope 23 of the X-ray tube. Sleeve 44 has about it a 2,141,soo

second sleeve 45 ot shorter length and made of lead or any other suitable X-ray absorbing material. The sleeve 45 is for arresting the primary radiation from the X-ray tube. An aperture 43 is formed at a suitable spot in the protective sleeve 45 to permit of the e of a cone o! useful X-rays from the tube.

The sleeves 44 and 43 are cemented together and to the casing i3. They are also held in po sition mechanically by means of a plug |33, having a turned down end which nts in the aperture 43 in sleeve 45. The plug |33 is held in position on the casing in a manner which will be explained later.

Spaces shown at 43a are provided between the container i3 and sleeve 45 to permit of the passage oi' oil from one section o! the container I3 to the other. 'Ihe insulating sleeve 44 supports at the end closest to the cathode o! the tube a support casting 45a.

Support casting 45a has within its inner surface lugs 43h for the purpose of supporting and locating an alignment plate 41 (see Figure 2), which is secured to the lugs 43h by means of screws 43. The alignment plate 41 has located within it three apertures 43 which are sumciently large to permit of the passage of the pins or contacts 31, 33, and 33 therethrough. The apertures 53 which are only large enough to permit the passage oi.' the necks 5i of the three pins or contacts 31, 33, and 33, are connected to the three apertures 43 by arcuate slots 32.

Because of this arrangement, the cathode end of X-ray tube Il may be pushed back inside the sleeve 44 until the pins 31, 33, and 33 register and pass through the holes 43 in the plate 41, after which the X-ray tube may be twisted, the necks 5i of the pins'31, 33, and 33 following the course ofthe slots 52. The pins or contacts 31, 33, and 33 are then held in engagement in the holes 53, the enlarged heads ot the pins preventing disengagement of the tube from the plate 41.

Circuits are then established to pins 31, 33, and 33 by means of the contact plate 53 which has three contacts 54, 55, and 53, complemental to pins 31, 33, and 33. Connections are made to contacts 54, 55 and 53 in a manner which will be described later.

The contact plate 53 floats on a stud 51 on plate 41. The contact plate 53 has an aperture 53 through which the stud 51 projects. The contact plate 53 is urged into contact with pins or contacts 31, 33, and 33 by means ot a spring 53. One end of spring 53 abuts the contact plate 53 and its other end engages end member 32 having a boss 33, the spring engaging the inner face of boss 33. 'Ihe end member or cover plate 32 closes the end of the sleeve 44 and is held in position by means of the screw 3| which is threaded into stud 51.

Protection against the radiation emitted from the end of the X-ray tube is had by means of rings 53 of suitable material which are held in position by means of a clamping ring 34 fastened by screws 35 (seeFlgure 5).

'I'he upper part of the enlarged section 43a' of the envelope terminates in a receptacle 13 through which conduits carrying current are carried to the interior of the enclosure or container i3. The current i'or energizing the several filaments of the tube and also the high tension current for the tube proper is carried by an insulated cable 1i shown in transverse section in "Figure 4.

In that figure, there is a plurality of wires 12 ,insideA the cable and insulated onefrom another.

The wires 12 carry one side of each of the separate filament energization circuits when a change-over switch for connecting either one filament or the other is exterior of the tube container I0, as is the case in the form of the invention shown in Figure 6.

In the drawings, only two conductors 12 are indicated; these to conform with the two-filament tube illustrated and herein described. If three laments were used in the tube, the series of l conductors 12 would comprise three separate elements; if four filaments, then four separate conductors would be shown, etc.

Spaced a slight distance away from the inner conductors 12 and insulated therefrom is a circle of smaller conductors 13. The conductors 13 are connected one to another and form a common lead for all of the various `filament circuits. The conductors 13, as can be seen, are spaced closely together to form as far as is possible a coronaproof surface and to reduce to a minimum the possibility of breakdown of the insulation. This is essential in the building up of cables for the voltages used. Irregular spacing or. misalignment of the conductors 13 may cause breake down at much lower voltage than is the case when the conductors 13 are evenly and regularly spaced in the manner described.

Surrounding the conductors 13 just described is a main insulating body 14 of corona-proof rubber or similar material. Exterior of body 14 is a metallic sheath 15 which is at ground potential and serves as an automatic safeguard against shocking the operator or patient should a breakdown of the insulation occur.

The cable just described and designated as a whole as 1| terminates within an insulating sleeve 16 (see Figure l). The sleeve 16 is sealed to the cable by means of an insulating material with which the end of the cable 1| to be placed within the sleeve 16 is coated after the metallic sheath 15 of cable 1| has been removed as is indicated at 11. The sleeve 16, at its lower end, has three connecting bushings 18.

The connecting bushings 18 comprise three studs 19 through each of which a small aperture 80 extends. The studs 19 are secured in position by means of nuts 8|. The free end of the conductors 12 and of conductors 13 are carried through the holes 80 in the studs 19 after which they are soldered as shown at 82. Connections are then made between the studs 19 and the contact posts 54, 55, and 56 upon plate 53 by means of several separate conductors 83.

The insulator 16 and the cable 1| are held in position on the casing 43a by a clamp 84 which surrounds the insulator 16 and is held in engagement with casing 43a by screws 85. A split brass sleeve 86 is soldered over the free end of the ground sheath 15 terminating at 11, and the cable 1| is clamped in position on the sleeve 86 at this point by means of scr-ew 81.

The reason for the particular structure just recited has its basis in the action of oil on rubber insulation, particularly when the oil is hot. When oil cornes into contact with rubber insulation an interaction takes place which destroys the rubber and causes a breakdown of the insulation. In the construction described, the sealing of the cable into insulating sleeve 16 prevents this interaction and So provides a structure having permanent insulating qualities.

A cable 90 extends to the anode. Cable 90 is similar in construction tov cable 1| except that only a single lead is used. The single lead comprises the inner and outer ring of conductors which are electrically connected so as to maintain them at the same potential. The combination of the several conductors is soldered to a conductor button 9| projecting from the end of the cable 90. An insulating sleeve 92 similar to sleeve 16 is attached to the cable 90. The insulating sleeve 92 has at its end a shouldered bushing 93. A plunger 94 projects from the lower end of bushing 93 and is maintained against movement entirely out of the bushing 93 by a shoulder 95. A spring 96 is compressed against the plunger 94 and is held on the bushing 93 by a threaded sleeve 91 which terminates in a prong 98 that grips and makes contact with the conductor button 9|. Thus current is carried from the several conductors in cable 90 to the spring actuated plunger 94 that makes contacting engagement with a radiator 99.

The object 0f radiator 99 is to rapidly absorb heat energy from the anode head I4 and to store such heat energy until it can be transmitted to the surrounding oil. It is important that this radiator be as 'large as possible, not only for the purpose of increasing its heat absorption capacity, but also to give it an outer diameter as nearly as possible equal to the inner diameter of the container, so as to reduce to a minimum the space between the radiator and the inner surface of the container. The surface of the radiator should be of substantially uniform curvature, without points or corners, and the radius of the curvature should be always as great as possible. The end sought by this construction is to increase as far as possible the transfer of heat from the radiator, through the oil and to the wall of the container, from which point radiation to the surrounding atmosphere takes place, while not decreasing the maximum operating voltage of the tube. The radiator is fastened to the anode shank |6 by means of a set screw |00. A thrust screw |0| is provided for releasing the radiator 99 from the anode shank |6 when it is desired to separate the two.

The open ends of the container |0 are closed by means of two caps |02 and |03, one of which is provided with a filling opening |04 sealed by means of a threaded plug |05. Caps |02 and |03 are held in place in any desired manner as, for instance, by means of screws |06.

An opening |01 is provided in container I0 for the passage of a useful beam of X-rays. Opening |01 registers with opening 46. The opening |01 is sealed against oil leakage by means of the plug |08, previously mentioned, which has a center section |09 of extremely thin material to reduce to a minimum the absorption therein of Xrays. The plug |08 is secured in place by any suitable sealing compound and is mechanically held in position by means of screws |09a which pass through a shoulder ||0 in the plug. Plug |08 also secures the sleeves 44 and 45 in position by extending into the aperture 46 in sleeve 45. Surrounding the plug |08 and the X-ray opening is a lead cylinder |92 which fits against the outer diameter of the lead sleeve 45, for the purpose of aiding the absorption of primary radiation from the tube The flaring sleeve which surrounds the plug |08 and projects from the main body of the container is provided for the purpose of mounting the entire structure on any of the standard tube stands. Within the flaring sleeve is an additional protection cone 93 fastened in position by means of the screws as shown. The cone is for the purpose of absorbing unwanted primary radiation.

The expansion of oii in the container Il presents a problem which is solved herein in two different ways. L j

The construction illustrated in Figures 1., 3, and 6, will be discussed first. In these figures. there is shown an oil expansion device having an outer casing generally made of sheet metal and terminating at one end in a nipple |2| which screws into threads |22 in the container Il surrounding the X-ray tube Il. An aperturey |23 extends through the center of the nipple `|2|, thus connecting the inner portions of the container |20 and of the tube container Il. Casing |20 has thereon and supports an expansion device of the so-called Sylphon or bellows type. The expansion and contraction device comprises an accordion-like metallic structure |24 that has soldered to it at the upper end of the container |20, a stud |25. The lower end of the bellows |24 has an inner stud |25 into which a rod |21 is screwed. The arrangement described maintains the bellows device in proper alignment at all times and provides in the rod |21 a calibration means |28 for indicating temperature conditions (in terms of pressure) within the X-ray tube enclosure |0. A spring |23 urges the4 expansion device to its expanded position.

When the tube is energized, insulating oil which fills the container |0 becomes heated as a result of the absorption by it of the heat energy of the tube. The oil expands under heat. The enlarged volume of the oil causes a portion thereof to push itself into the container Y,

|20 to contract the expansion vand contraction bellows |24 against the action of the spring |20. Rod |21 is forced upwardly out of container |23 a greater distance as more oil forces itself into envelope |20. When the tube is deenergized, the oil cools. The urge of spring |29 expands the expansion and contraction device |24, thus compensating for the reduction in oil volinne and maintaining the container I0 about the tube free of voids. Freedom from voids is a condition essential for the safe operation of an X- ray tube.

The second form of device for compensating for oil expansion is shown in Figure '7 and comprises a container |30 connected to the container i0 by means of a flexible tube |3|. When a container |30 is employed, an oil level guage |32 is generally employed. The container |30 has a filling opening |33 closed by a plug |34 that contains an air vent |35 for relieving air pressure in tank |30.

The question of weight is of the greatest influence in deciding between the two methods just described for application to a specific installation. Where ease and rapidity of adjustment is of the greatest importance and some sacrifice of range can be made, the structure with the separate container is usually provided. If range is the prime essential the structure shown in Figures 1 and 6 is used. In this way, means are provided whereby the best possible combination for any particular purpose can be had while using a common basic construction.

One of the most diilicult problems with respect to tubes of the variety illustrated is the proper alignment of the X-ray tube with the opening in casing l0 for the passage of useful X-rays. Deviation from proper alignment can be in two directions, namely. longitudinally of the ing, that is, in a direction parallel toths main axis of the tube, or axially, that is, the tube may be improperly positioned in angular direction when considering the longitudinal axis of the tube as the center of rotation. Possibility of both of these errors is avoided in the construction illustrated.

Accurate longitudinal adjustment of the tube in the containery is provided for by the cathode cap 35 and plate 36a. During the manufacture of the tube, the base may be adjusted back and forward on cathode arm 21 until a proper position is obtained. In practice, aA certain dimension is set up as being accurate for spacing the center of the anode button I5 from some predetermined point onthe plate 36a. 'Ihe plate 35a is positioned in accordance with this dimension. Plate 35a and cap 35 are properly positioned angularly and the cap 35 with plate 35a attached is cemented in place.

Axial registry of tube and casing is provided for by the structure shown in Figure 2.V It is a simple matter to position the pins or contacts 31, 33, and 35 in a definite relation to the cathode openings 34 and 35 in the cathode |3'by moving plate 35a on cap 35, screws |50 moving in slots |5| to permit the shift. In the same fashion, the support casting a can be definitely positioned in respect to bakelite sleeve 44 which in turn is held in a definite relation with respect to the X-ray opening 45 by plug |03. The line thus obtained deiinitely positions the alignment plate 41 which determines the angular position of the tube when in operable position.

Selection and energization of anyone of the several filaments in the X-ray tube may be had in one of two methods. These are shown in detail in Figures 6 and 1.

Figure 6 illustrates a structure in which the switching mechanism is external of the tube. In Figure 6, a transformer is illustrated and is the source of a high tension current.

One terminal of secondary |5| of transformer is connected through cable 30 to the anode |2 of X-ray tube The other terminal of transformer |50 is connected through cable 1| to the cathode I3 of X-ray tube A filament current transformer |52 is also shown. Sec- `ondary |53 of the transformer |52 is connected at one end to a pivot point |54 in a movable contact |55 of a. hand-operated switch mechanism |56. The other terminal of the secondary |52 is connected to one terminal of secondary |5| and from thence to a common lead |51 for both filaments in the tube.

The outer lead of one of the filaments |50 is connected through cable 1| to a resistance |59 and thence to a contact |50 of the switch mechanism |56. The other terminal of the other filament |5| is connected to another contact |62. An insulated pusher bar |63, actuated in any desired fashion as, for instance, by a cord system, is arranged to move the movable contact |55 from one point to the other as desired. From this it can be seen that either one of the two filaments provided can be selected for' operation. The bar |63 may be used to indicate which filament is lighted.

'I'he filament current switch |55 may be located wherever desired. It is generally hung in the filament transmission system at the end of the cable 1| This, however, is immaterial, and it could be interposed in any point in this cable `lust as readily.

When a separate selecting switch is thought undesirable, an arrangement similar to that shown in Figure 7 may be employed. Only two leads are carried to the cable 1|. In this device, n high tension transformer |10 supplies high tension current for energizing the X-ray tube Il. Secondary 1| in the high tension transformer |10 has one terminal connected through cable 9U to the anode I2 of the X-ray tube |I. The other terminal is carried through cable 1| to the anode lead |13 of the tube' filaments in the X-ray tube.

A filament current transformer |14 is provided for supplying filament current. The secondary |15 of the filament current transformer has one side connected in common to one terminal of the high tension secondary and is with this ter.- minal connected to the lead |13 of the two fila.- ments. The other terminal of the filament current transformer secondary |15 is connected to the two upper contacts |16 of the switch mechanism |11. One lower contact |18 ls connected to the other terminal of one of the filaments, as shown at |19 through resistance |19a. The other lower contact is connected to the remaining terminal of the other filament as shown in |8|.

The movable member of the switch consists of an insulating pusher rod |82 provided with a conductive cylinder |83 arranged to connect con-f tacts |16 and |18 or contacts |16 and |80 together in order to select the desired filament for the operation. Actuation of pusher rod |82 is had through accordion-like expansion and compression devices |86 and |85 secured to the outer casing of the tube at opposite ends of ro |82. f

'I'he expansion and contraction devices |84 and are secured to the casing to provide oiltight joints between the casing and said expansion and compression devices and at the same time, through the medium of their expansibility and compressibility, to permit of the actuation of the pusher rod |82 for selectively establishing the desired filament circuit. For this arrangement, only two conductors need be brought down the cathode cable, and no auxiliary mechanisms exterior of the tube are required.

From the foregoing, it is seen that there has been devised an X-ray tube which is entirely enclosed within a grounded metallic casing. Danger of electrical shock thus is avoided. X-ray protection has been provided in the form of a lead cylinder about the body of the X-ray tube and in rings made of lead impregnated insulating material about the anode and cathode arms of the tube. In order to reduce thc size of the container, oil has been supplied as a dielectric. Two different methods are illustrated for taking care of the unavoidable expansion of the insulating oil due to increases in temperature of the oil during operation of the X-ray tube. Means have been disclosed whereby the X-ray tube can be readily positioned lengthwise of a casing and in correct axial direction thereto to permit accurate registration of the focal spot of the tube with an aperture in the casing for the passage of radiation. A novel method of bringing in the high tension current to the X-ray tube has been provided. The X-ray tube shown is of the double focus type. Two methods for selecting the filament of such X-ray tube to be energized have been disclosed, one of these being with the selector switch at the exterior of the casing, and the other with the switch an integral part of the casing.

What is claimed as new and is desired-to be 1.-In combination, an X-ray tube, an X-ray transparent vsecured by Letters Patent of the United States is:

insulating sleeve fitting closely -thereabout, a sleeve of material opaque to X- light about said insulating sleeve and having an v high tension conduits from said high tension transformer to said anode and cathode, two filaments in said cathode, a filament current transformer, a first filament current conduit from one terminal of said filament current transformer common with the high tension conduit to said cathode and common to both of said filaments, a second filament current conduit from said filament current transformer, third and fourth filament current conduits each leading to a different filament, switch means for selectively connecting the second of said conduits to said third and fourth conduits to determinev the filament to be energized, and a casing for enclosing said tube and said switch.

3. In combination, a high tension transformer, an X-ray tube, having an anode and a cathode, high tension conduits from said` high tension transformer to said anode and cathode, two filaments in said cathode, a filament current transformer, a first filament current conduit from one terminal of said filament current transformer common with the high tension conduit to said cathode and common to both of said filaments, a second filament current conduit from` said filament current transformer, third and fourth filament current conduits each leading to a different filament, switch means for selectively connecting the second of said conduits to said third and fourth conduits to determine the filament to be energized, a casing for enclosing said tube and said switch, an operating rod for said switch traversing said casing, and compressible means on said casing enclosing the ends of said rod.

4. In the combination of claim 3 wherein the compressible means comprises closed end bellows sealed upon the side of said casing and enclosing the ends of said rod projecting from said casing.

5. In combination, an X-ray tube having an anode and a cathode, a casing for said tube, said casing having an X-ray transmitting window portion, a cap on said tube at a predetermined distance from said anode, contact members carried by said cap, a holding member, and means for supporting said holding member on said casing in a predetermined position and at a predetermined distance from said window portion, said holding member having arcuate apertures to slidingly receive said contact members upon partial rotation of said tube whereby the anode is properly alined relative to the window portion of the casing and said tube is locked against axial movement relative to said casing.

6. The combination as dened in claim 5 and in which the contact members carried by the cap have enlarged heads, and the arcuate apertures in said holding member are each enlarged at one end toreceive one of said enlarged heads.

-casing having an X-ray transmitting window portion, a cap on said tube at a predetermined distancefrom said anode, contact members carried by said c ap, a holding member, means for supporting said holding member on said casing in a predetermined position and at a predetermined distance irom said window portion, said holding member having arcuate apertures to slidingly receive said contact members upon partial rotation of said tube whereby the anode is properly alined relative to the window portion of the casing and said tube is locked against axial movement relative to said casing, and a terminal plate loosely mounted on said holding member andl having a plurality of contact members adapted to engage the contact members on said cap when said tube is in locked position.

8. In the combination dened in claim 7 wherein resilient means are provided for retaining said terminal plate on said holding member and for normally urging the contact members on 'said terminal plate into engagement with the contact members on said cap.

9. In combination, any X-ray tube comprising an envelope and an anode and a cathode in said envelope, a casing for said tube, said casing having an X ray transmitting window portion, a dielectric sleeve interposed between said casing and said tube, a cap on the cathode end portion of said tube at a predetermined distance from the anode, contact members on said cap, a supf porting member carried by said sleeve adjacent one end thereof and spaced a predetermined distance from the X-ray transmitting window portion of the casing, a holding member having arcuate apertures to slidingly receive said contact members, said arcuate apertures each being enlarged at one end to freely receive said contact members whereby upon insertion of said contact members into said apertures, and upon partial rotation oi said tube, the anode is properly alined relative to the window portion of the casing and the tube is locked against axial'movement relative to said casing.

10. In combination, an X-ray tube comprising an envelope and an anode and a cathode in said envelope, a casing for said tube, said casinghaving an X-ray transmitting window portion, a dielectric sleeve interposed between said casing and said tube, a cap on the cathode end portion of said tube at a predetermined distance from the anode, contact members on said cap, a supporting member carried by said sleeve adjacent one end thereof and spaced a predetermined distance from the X-ray transmitting window portion oi' the casing, a holding member having arcuate apertures to slidingly receive said contact members, said arcuate apertures each being enlarged at one end to freely receive said contact members whereby upon insertion of said contact members into said apertures, and upon partial rotation of said tube. the anode is yproperly alined relative to the window portion oi the casing and the tube is locked against axial movement relative to said casing, a terminal plate having contacts adapted to engage the contact members on said cap when said tube is locked in position, and a cover secured to said terminal plate and enclosing that end of the'dielectricsleeve, conductor members passing through said casing, said sleeve having an opening therein adjacent said cover for permitting passage lof said conductor members into the housing formed by said sleeve and said cover for connection with said terminal plate.

11. In combination, an X-ray tube, a` metal casing for enclosing and supporting said tube, X-ray opaque and X-ray transparent sleeves interposed between said. casing and said tube and in engagement with said tube and casing for supporting said tube upon said casing, said casing and said X-ray opaque sleeve having registering apertures to permit the emission of a useful beam of X-rays from said X-ray tube, a plug secured to said casing and extending into the aperture in said opaque sleeve for retaining the opaque sleeve and casing in proper alinement, said plug having an X-ray transparent window therein in alinement with the registering apertures in said casing and opaque sleeve, and said X-ray transparent sleeve being oi insulatory material and having a portion extending across the opening in said opaque sleeve and said casing.

12. 'I'he combination of claim 11 including an insulating fluid in said casing, said casing having a groove extending circumierentially partially about said opaque sleeve and axially thereof the iull length of said opaque sleeve to form a passage permitting free circulation oi' the insulating iiuid from end to end of the casing.

13. In combination, an X-'ray tube having an envelope, a casing enclosing said envelope, laxninations oi electrically insulatory and noninsulatory material interposed between s aid casing and said envelope, one of said laminations of the casing being opaque to X-light and having a window for the emission of a beam of useful X-light and another lamination being closely circumjacent said envelope and of a dielectric material transparent to X-light, said dielectric lamination having a continuous extension across the window formed in the opaque lamination, through which extension the beam of useful X- light is projected, said casing having an opening therein in registry with the opening in said opaque lamination and a plug having an X-ray transmitting window therein, said plug being secured to said casing and extending into the opening in said casing and the opening in said opaque lamination for retaining the opaque lamination and casing in proper alinement.

MALVERN J. GROSS. ZED J. ATLEE. 

